I'm pretty new to vaping spice, but I've done ayahausca and loads of mushrooms so hopefully my ritual with those things can help you out.
First, I like to take a long shower. I tend to get very self-conscious and see myself dirty spiritually. It also gives me time to defrag, and mentally prepare for the journey. Bathing during a psychedelic journey really helps me shed accumulated negativity and leave my worldly problems behind. I don't think that this would be a good idea during a spice trip, but I recommend it for ayahausca though.
Then, I relax for a while wherever I plan on tripping. This helps me get comfortable with my environment and ensures that I wont run into unexpected problems during the experience. Ant colonies and beehives aren't something you notice right away lol. During this time, I listen to good vibe music (typically George Harrison) and burn some sage; blowing it all around the environment. I mentally try to uplift the energy around me and I cleanse myself with the sage smoke.
Sometimes I do yoga. I've noticed it helps calm me down, but I typically forget beforehand. I always pray/state my intentions. That strengthens my will power and gives me the nerve to do a large dose.
One of the quirky things I do before hand is walk counter-clockwise seven times around the tripping space. Counter-clockwise because that's the way the universe is is expanding. And 7 revolutions because I live in the third dimension, and seven dimensions separate me from the 10th dimension. I usually feel altered and higher intellectually after I do this, but it could simply be placebo. I got this idea from the Muslims. They walk around the Kabba in Mecca 7 times, to uplift themselves so they can appreciate and see Gods glory, or something along those lines.
I also like to drink some sage tea beforehand. It sharpens my mind, which helps me understand the psychedelic world. I'm pretty sure sage's nootropic properties aren't placebo. After all, really wise people were called sages back in the day. I'm pretty sure these two things correlate.
It's taken me a while to find out what is right for me. This ritual truly is a ritual, and throughout the whole process I'm paying my respects to myself, the psychedelic world, God, and nature. I think respect is paramount when dealing with psychedelics. It really sucks when nature, or the beings in hyperspace don't respect you. So, good luck and safe travels!
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I hope this helps you on your journeys!
Here's a useful diagram on DMT usage I nicked from one of endlessness's posts.
https://www.dmt-nexus.me/users/house/DMTDiagram.png House did a good job on this one